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21.
An analysis of the range of morphology among arthropods demonstrates that disparity among living arthropods is similar to that in Cambrian arthropods. The range of morphological design resulting from the Cambrian "explosion" has been overestimated, reflecting a tendency to separate as "problematic" taxa that cannot be accommodated in the classification on the basis of the living biota. Problematic taxa are largely an artifact of an inadequate taxonomy. Special evolutionary processes may not be necessary to explain the early radiation of the metazoans. 相似文献
22.
Wills D 《Science (New York, N.Y.)》1987,238(4834):1740-1741
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JH Golden FJ DiSalvo JMJ Frechet J Silcox M Thomas J Elman 《Science (New York, N.Y.)》1996,273(5276):782-784
The preparation and analysis of inorganic-organic polymer nanocomposites consisting of inorganic nanowires and multiwire "cables" in a random-coil organic polymer host is reported. Dissolution of inorganic (LiMo3Se3)n wires in a strongly coordinating monomer, vinylene carbonate, and the use of a rapid polymerization in the presence of a cross-linking agent produce nanocomposites without phase separation. Polymerization of dilute solutions yields a material containing mostly (Mo3Se3(-))n mono- and biwires, 6 to 20 angstroms in diameter and 50 to 100 nanometers long. Polymerization of more concentrated liquid crystalline solutions yields a nanocomposite containing oriented multiwire cables, 20 to 40 angstroms in diameter and up to 1500 nanometers long, that display optical anisotropy and electrical conductivity. 相似文献
24.
H Thompson I A McCandlish H J Cornwell L Macartney N S Maxwell A F Weipers I R Wills J A Black A C Mackenzie 《The Veterinary record》1988,122(16):378-385
The performance of three live attenuated feline parvovirus vaccines licensed for use in the dog was studied. At the end of the primary vaccination course 67 per cent of dogs had inadequate antibody levels (less than or equal to 32) as measured by a haemagglutination inhibition test. Interference by maternal antibody accounted for some of the failures but the fact that there was no significant difference in performance between dogs vaccinated at 12 weeks or 16 weeks of age indicated that maternal antibody was not the only factor. 相似文献
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Butylated hydroxytoluene (BHT) was found to be effective in reducing the incidence of superficial scald in ‘Granny Smith’ apples grown in Australia and New Zealand, when it was applied to the fruit as a post-harvest dip or when the fruit were stored in wraps impregnated with BHT. However, much higher concentrations of BHT were required to produce an equivalent reduction in scald compared with diphenylamine or ethoxyquin. 相似文献
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